Tissues Flashcards
What is a membrane?
It is the envelop of an organ that is thin and “fluid”.
Of what is composed the membrane structure?
Of a bilayer phospholipids, of sterol lipids and proteins.
What is the composition of the phospholipids?
They have a hydrophobic tail and a hydrophilic head.
Why to the phospholipids form a bilayer?
Because the hydrophobic tails repeal water and the hydrophilic heads are attracted to water. Since the cells are mostly in aquous solution, the tails tend to regroup together and the head tend to attach to the water molecules.
What kinetic do the phospholipid have?
They are in constant movement in the same plane.
How are called the sterol lipids in animals and in plants?
They are cholesterol in animal cells and phytosterol in plants.
What is the purpose of sterol lipids?
They stabilize the membrane. The sterol lipids fit between the fatty acid chain and keep a certain fluidity to the chain.
In with digestional juice are sterol lipids important?
They are important in the synthesis of the bile.
What is the purpose of proteins in the cell membrane?
They make the channels.
What are the different types of proteins on the membrane cell?
- integral membrane protein
- trnasmembrane proteins (lactose permease)
- Peripheral membrane
In order from the smallest to the biggest, give the molecules present on the cell membrane.
phospholipids, sterol lipids, proteins
What are the 7 membrane functions?
- define cell
- selective transport
- enzyme activity
- signal transduction - proteins receptors
- cell adhesion - celle to cell links
- cell recognition
- attachment to cytoskeleton
Why can the function of cell variate from one to an other?
Because of the proteins present on the membrane.
FOr what are proteins receptor used in the cell membrane?
To transfer a message from outside to inside of the cell. These proteins are often hormones.
When will one find more cell to cell links?
In organs that have to expand a lot .
What are the 3 names of passive tranport in cells?
- diffusion
- osmosis
- facilitated diffusion
What is diffusion?
It is the movement of particules down concentration gradient.
What is the gradient?
The “slope”. Down gradient means that it goes from high concentration to low concentration.
What molecules can diffuse through the membrane?
They are small and non-polar molecules.
H2O, O2, CO2, N2, hydrophobic molecules, lipid-soluble molecules
What is osmosis?
It is the pasive tranport of water through the molecule by aquporin channels. It goes from a hypotonic (low in salt) to a hypertonic (high in salt) environment until both environment are isotonic.
What are aquaporin channels?
They are protein imbeded in the membrane that allow water go trhough. They let more water molecule in than if there was only the bilayer.
What is an example of osmosis in plants?
Turgor pressure
